Improvement in screw-propellers



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Letters Patent No. 93,848, dated August l17, 1869 IMPROVEMENT IN SCREW-PROPELLERS.

The Schedule :referredl to in these Letters Patent and making part of the same.

To whom it may conce/ru:

, Be it known that I, FREDERICKWITTRAM, of the city and county of San Francisco, in the State of California, have invented certain neiv and useful Improvements in Screw-Propellers; and I -hereby declare that the following is a full, clean, and exact description thereof, reference being made to the accompanying drawings, making part of this specification, in which- Figure l is a front view of a two-armed screw-propeller, ready for use;

Figure 2, a side View of fig. l

Figure 3, a front view of the same propeller; when not required for propulsion; and

Fignre`4, a side view of iig. .3.

The letters of reference indicate the same parts in the different igures.

My invent-ion relates to propellers which are used as auxiliaries to sailing vessels or on canal-boats, and has for its .object what may be called reeling or reducing the area of the resisting surface of the propeller, when the vessel is moved by wind, or other means than power applied to the screw-shaft, without resorting to anyof the expensive or complicated methods of elevating the screw, now in use.

To accomplish the desired end, I construct a screwpropeller of any desired form or pitch, in two or more vertical sections, perpendicular to the axis of rotation. In the present instance, I divide Vit into three parts, a, l), and c. One of these is keyed or otherwise fixed t0 the shaft d, the others are made to Ivork freely upon the shaft.

IVhen the propeller is to be used to propel the vessel, the several parts, a, b, and c, are secured together lby any convenient means forming a complete, screwpropeller, as shown in figs.v 1 and 2.

NVhen sails are used, the sections are disengaged and secured together in aline with each other, as shown in figs. 3 and 4, presenting a min'imum of sulface of resistance to the'` passage of the water aft.

vlhe sections, in thc present instance, are secured together in either of the above-mentioned relative positions, by a bolt, e, working in a groove in the shaft d, aud carrying studs t',`\vhich, when the bolt is forced aft from the interior of the vessel, or in any other convenient manner, take into suitable gains or notches in the hubs of thesections.

\Vl1en the bolt is Withdrawn to a proper distance, the studs enter into annular grooves in thehubs, which permit free revolution of the sections in changing their relative positions.

I do not limit. myself to sections of any particular.

form of what is known as the screw-propeller, nor to thev number of arms or blades used,or sectionsinto which it may be divided, nor to any special devices for securing said sections in position; but

XVhat I claim as my invention, and desire to secure by Ietters Patent, is y The propeller A, when constructed in two or more sections, and so arranged, in connection with the bolt e or its equivalent, that the sections can be secured together' upon the shaft d, forming a complete whole, or ina line with 'each othersubstantially as described, for the purpose of decreasing the area-of resistance to the water, as set forth.

FREDERICK WITTRAM.

Witnesses G. GAITHER, EDM. E. BROWN. 

